1. Field of the Invention
The invention is in the field of machines for producing braided structures useful inter alia as reinforcements for composites.
2. Description of the Related Art
The braiding process is one of the traditional methods of interconnecting strands of fibers into fabrics, ropes and tubes.
In the braiding process, yarns are normally fed through a machine where they are caused to interlace with each other to form various braided structures. Such structures, following their early use in the reinforcement of hoses such as fire hoses, have become increasingly important in the reinforcement of so-called composite structures of various shapes and uses.
The usual braiding machine interlaces yarns as follows. Braiding yarns, wound on bobbins, are carried on a carrier which is said to `float` with respect to the rest of the machine because they are not permanently attached to the rest of the machine. Typically a plurality of carriers move in intersecting paths in the braiding plane, generally half in each direction. The result is that the `free` ends of the yarns are interlaced over and under other yarns at the braid formation point The carriers are generally propelled in guiding slots by means of notched disks called `horn gears`. Rotating close together in opposite directions, the gears pass the carriers from one gear to another. Such a system is shown, for example, in U.S. Pat. No. 3,981,223.
The carriers usually move in a roughly horizontal plane, usually called the braiding plane. The point at which the braid is assembled, called the braiding point, lies above the plane.
However, it is not necessary to the functioning of the braider that the braiding plane be horizontal and that the braiding point be above the plane. U.S. Pat. No. 4,304,169 shows a braiding machine wherein a series of alternate braiding planes and braiding points are arranged in a horizontal configuration. The invention of this application can be applied to any single or series arrangement regardless of the orientation of the device.
The term `yarn` as used herein is intended to comprise all forms of yarn, synthetic or natural, organic or metallic of any cross section.
Naturally, as in most active arts, many variations are known and practiced. For example, it is common practice to enclose so-called axial yarns in braided structures. Axial yarns are yarns which are simply fed into the braided structure without themselves being interlaced about other yarns; they are held in place by yarns which are interlaced as described above.
Since the bobbins move with respect to the braiding point, means are usually needed to maintain approximately constant tension in the yarn leaving the bobbin and to take up yarn when the bobbin moves in the direction of the braiding point. This is variously accomplished, e.g. by providing a spring loaded idler wheel to each yarn combined with a pawl to prevent excessive unwinding from the bobbin.
Common to most commercial braiders is a high degree of mechanical complexity and specialization such that a particular machine is often capable of producing only a single braiding design without extensive modification.